The Caleffi XS under-boiler magnetic filter mechanically separates the impurities in heating and cooling systems by means of a mesh filter, a neodymium magnet and a collection chamber for the heaviest particles.The chamber has transparent windows, allowing the user to check whether the internal elements need to be cleaned. It’s small dimensions make it suitable most types of boiler of heat interface unit (HIU). Caleffi XS Filter - 22mm